1. Field of the Invention
The present invention relates to a recording apparatus, and in particular to an impact type recording apparatus which effects recording by the impact force of a recording hammer.
2. Related Background Art
In the field of a recording apparatus for a computer system or an electronic typewriter, there is generally known a so-called impact type recording apparatus such as a daisy wheel printer. The recording apparatus of this type is designed chiefly such that a hammer or the like is driven by a magnetic force produced when electric power is supplied to a solenoid, and impacts characters to thereby accomplish printing, and such recording apparatus has the merit that printing of high quality can be obtained, while it has the demerit that the noise during printing is great. One of the causes of the noise is the impact sound produced when the hammer returns to its standby position and strikes against a stopper after printing. A method of reducing such noise is to supply electric power to the solenoid when the hammer returns to a predetermined position, and reduce the return speed thereof to thereby reduce the sound of impact against the stopper.
Generally, however, the areas of the characters included in the character wheel differ from one another and the printing energy necessary for printing also differs from character to character and therefore, the power supply time or the energizing current value of a coil unit for driving the hammer is controlled to thereby control the kinetic energy imparted to the hammer. For example, control is effected such that the hammer speed when printing a character of large printing area such as "M" is fast and the hammer speed when printing a symbol of small printing area such as "." is slow.
Therefore, in situations where an attempt is made to decelerate the printing hammer by the aforedescribed method and the energization timing is set so that as shown in FIG. 7A of the accompanying drawings, the deceleration is completed the hammer returns to the stopper. The deceleration corresponds to a curve 60 showing the displacement of the hammer when printing "M". The timing of the energization for deceleration will become too early in the case of a curve 61 which shows the printing of ".", and the brake will act before the hammer returns to the stopper, and thus the hammer will advance toward the platen (the portion indicated by 62). Also, if as shown in FIG. 7B of the accompanying drawings, the energization timing is set correspondingly to a curve 63 which shows the printing of ".", when the character "M" is printed, the hammer strikes against the stopper at 65 before it is decelerated as indicated by a curve 64, and thus a sufficient effect cannot be obtained.